I'd like to see the digitizer expanded with a 1:1 'fixed mode' option that represents an equal resolution, fixed portion of the screen. That way it could be used better for drawing.
Preferably the PC would also be able to transmit an image of what was on its screen to the adam. For drawing purposes this doesn't need to be high refresh rate, just enough to get your position to know where to put your finger/stylus down. To move the portion being displayed a two finger drag could be used.
Beyond that, if the refresh rate were high enough, it would be good for remote desktop as well at that point. If that were the case, I'd like to see some different zoom modes if not too cpu intensive. When viewing the desktop on the adam, a fully zoomed out mode, which would show the full screen of whatever was on the desktop, scaled if necessary, regardless of resolution. Then the ability to pinch zoom, which would snap when it hits a 1:1 resolution ratio. Since the monitor is probably higher res, this would only show a portion of the screen on the adam. Two finger screen panning should be possible at this point. Single finger just controls the mouse like normal. After that it should still be possible to zoom in even more, just like desktop zoom on ubuntu with compiz/beryl.
Although I can't see any purpose for skew/stretch, it would be fun if that were possible using a 4 finger zoom (2 fingers from each hand). Just as a bonus, hehe.
I suppose it depends how good the vector/pixel mapping graphics can be.